CN116349085A - Apparatus for multiplexing or demultiplexing polarized waves - Google Patents

Abstract

The present invention provides a dielectric waveguide for spatially separating two orthogonally polarized components of an electromagnetic wave from each other or forming an electromagnetic wave having two orthogonally polarized components by spatially combining two linearly polarized electromagnetic waves. The dielectric waveguide includes a first branch for carrying a first linearly polarized wave and a second branch for carrying a second linearly polarized wave. The dielectric waveguide includes a dual polarized port including a first region and a second region. The first and second regions of the dual polarized port are a cross section of the first branch and a cross section of the second branch, respectively, the first and second regions partially overlapping.

Description

Apparatus for multiplexing or demultiplexing polarized waves

Technical Field

The present invention relates to multiplexing and demultiplexing polarized signals for transmission in a dielectric waveguide cable.

Background

Communication over dielectric waveguide (dielectric waveguide, DWG) cables (also known as polymer microwave fibers (polymer microwave fibre, PMF)) is one of the options for filling the performance gap between copper links and optical high speed data links in mid-range applications. The combination of millimeter wave transceiver chips (30 GHz-300 GHz frequencies), small antennas, and inexpensive plastic optical fibers provides a robust, cost-effective, and low weight high-speed communication link for a variety of applications. Dielectric waveguides have lower losses than copper and can achieve higher bandwidths. Dielectric waveguides are a cheaper, more mechanically robust technology than optical fibers. See Maxime De Wit; simon Ooms; bart philippipe; yang Zhang; patrick Reynaert; "Polymer microwave optical fiber: new methods of converged wireline, optical, and wireless communication (Polymer Microwave Fibers: A New Approach That Blends Wireline, optical, and Wireless Communication) "; IEEE microwave journal; roll 21/1 in 2020.

As with other communication technologies, polymer microwave fiber (polymer microwave fiber, PMF) communication may be established over multiple orthogonal transmission channels to improve data throughput or support duplex communication. In a single PMF, orthogonal transmission channels may be implemented by two polarizations of the optical modes (e.g., fundamental modes) of the PMF. Two signals having mutually orthogonal polarizations are also referred to as spatially orthogonal signals. To achieve this polarization diversity, quadrature analog converters (orthomode transducer, OMT) are required. OMT is a waveguide polarizer device with three physical ports. In the context of the art, the term "port" refers to a cross section of a waveguide, or a cross section of a branch of a waveguide. In the present invention, a cross-section of an optical element (e.g. a cross-section of a waveguide or a cross-section of a branch of a waveguide) is understood to be a cross-section perpendicular to the main propagation direction of a wave (or signal) propagating in the optical element (i.e. a notch), i.e. a notch perpendicular to the optical axis of the optical element. The ports are not necessarily located at the ends of the waveguides. The function of OMT is to separate or combine two spatially orthogonal signals in the same frequency band simultaneously. OMT is also known as quadrature mode junction, polarization diplexer, or dual mode converter.

Existing OMTs for PMF communication are typically dual polarized coupler (antenna) designs. Such designs achieve polarization selective coupling through coupler geometry. Such designs are used, for example, for patch antennas. See, for example:

meyer a, schneider m., "robust design of broadband dual polarization transition from PCB to circular dielectric waveguide for millimeter wave applications (Robust design of a broadband dual-polarized transition from PCB to circular dielectric waveguide for mm-wave applications)"; international journal of microwave and wireless technology 12, 559-566, 2020;

U.S. Dey and J.Hesselbarth, "Millimeter wave Chip-to-Chip interconnect (Millimer-wave Chip-to-Chip Interconnect Using Plastic Wire Operating in Single and Dual Mode) operating in both single and dual modes using plastic wire", IEEE/MTT-S International microwave seminar-IMS, 2018;

yu B, ye Y, ding X, liu Y, xu Z, liu X and Gu QJ' orthogonal mode sub-terahertz interconnect channels for planar chip-to-chip communications (Ortho-mode sub-THz interconnect channel for planar chip-to-chip communications) "IEEE microwave theory and technology journal, 66, 1864-1873, 2018.

There are four major disadvantages to this geometry-based coupler. First, dual polarized coupler designs typically have complex, cumbersome shapes. It is difficult to integrate into a printed circuit board or chip package. Second, inducing separate polarization is challenging. To support dual polarization, the coupler design may compromise the performance of the individual polarizations. Third, the coupling efficiency relies on the manufacturing repeatability of the coupler structure to achieve good isolation. Fourth, when the substrate, frequency band or bandwidth changes, the coupler structure needs to be redesigned.

Existing PMF OMT coupler designs implement orthogonal transmission channels in various ways. In one example, PMF OMT implements polarization selectivity using stacked patch coupler topologies. If multimode DWG is used, the transition between the microstrip line and the circular dielectric waveguide may be achieved by a DWG port structure that acts as a high order mode filter. This design has no polarization dependent function. Polarization selectivity is achieved only by the geometry of the coupler design. In another example, PMF OMT utilizes a combination of parasitic patch topology, dielectric spheres and metal holes to achieve polarization selectivity. Likewise, polarization selectivity is achieved only by the geometry of the coupler design. In yet another example, the PMF OMT implements polarization selectivity using a differential probe topology. Likewise, polarization selectivity is achieved only by the geometry of the coupler design.

In an alternative to the coupler design-based approach described above, the configuration of the interface between the electromagnetic component and the antenna (e.g., in the form of a patch or probe) imparts orthogonal transmission channels for polarized waves, creating OMT holes using metallic waveguides. The design relates in particular to polarization-selective coupling interfaces between two metal waveguides. The polarization-selective coupling interface is for allowing a horizontally polarized signal to pass between a first linear propagation path and a second linear propagation path of the two waveguides, but preventing a vertically polarized signal from passing between the first linear propagation path and the second linear propagation path. The result is polarization selectivity at the interface of the vertical plane between two different metal waveguides.

All OMT designs described above rely on designing the coupler itself for dual polarization. That is, the cross shape of the multiplexed signal is formed by physically crossing antennas.

It is desirable to develop an OMT that can provide dual polarized waves to a dielectric waveguide cable while avoiding additional coupling losses between the connector and PMF, has mechanical robustness, has high coupling efficiency, and is flexible so that modifications to the design are minimized when used over a range of substrates, frequency bands, and bandwidths.

Disclosure of Invention

According to one aspect, there is provided a dielectric waveguide for spatially separating two orthogonally polarized components of an electromagnetic wave from each other or forming an electromagnetic wave having two orthogonally polarized components by spatially combining two linearly polarized electromagnetic waves, the dielectric waveguide comprising a first branch for carrying a first linearly polarized wave and a second branch for carrying a second linearly polarized wave, the dielectric waveguide having dual polarized ports comprising partially overlapping first and second regions, the first and second regions being a cross section of the first and second branches, respectively. The term "port" refers to a cross-section of a waveguide or a cross-section of a waveguide branch. Obviously, the port may be a cross section at the end of the waveguide. A cross section of a portion of the waveguide is understood to be perpendicular to the main propagation direction of the electromagnetic wave in the corresponding portion of the waveguide. In other words, the cross-section is a cut in the transverse plane (rather than the longitudinal plane) of the respective portion. The waveguide provides a simple and effective method of multiplexing or demultiplexing electromagnetic waves.

Dual polarized ports may have C4 symmetry. Dual polarized ports may have D4 symmetry. Waveguide symmetry supports the highly symmetric nature of electromagnetic waves and improves the transmission characteristics of the waveguide. D4 symmetry has the additional advantage that dual polarized ports can have two orthogonal reflection axes, and thus, waves can be symmetrical (i.e., invariant) under geometric reflection of either of these two axes.

The first and second branches may each have an elongated (e.g., rectangular, oval or elliptical) cross-section. The elongated cross-section helps to carry a first polarization component and repel a second polarization component orthogonal to the first polarization component.

The first and second branches may be gradually spatially separated from each other. This helps to minimize distortion and loss of the wave when it is demultiplexed.

At least one of the cross-section of the first branch and the cross-section of the second branch may be progressively rotated in space. Thus, the polarization vector of the wave in the first branch and/or the polarization vector of the wave in the second branch gradually rotates in space as the wave propagates in the respective branches. In one embodiment, when two waves propagate in two branches, the polarization vector of the first branch and the polarization vector of the second branch are rotated relative to each other, thereby minimizing distortion and loss, while achieving orthogonal polarization in the dual polarized port, and parallel polarization, for example, in two branches at a location remote from the dual polarized port.

The first and second branches may be symmetrical to each other under reflection through the plane of the dual polarized port. Thus, the two polarization components can propagate symmetrically, and characteristics such as loss, dispersion, and polarization can remain similar in the two branches.

The ports of the first branch and the ports of the second branch may be spatially separated. This facilitates the complete separation of the two orthogonally polarized components of the electromagnetic wave. It also helps to connect the waveguide to two spatially separated devices, one for each component.

The ports of the first branch and the ports of the second branch may be identical and have the same orientation. Thus, two ports may be particularly suitable for receiving or transmitting two waves having the same polarization. In this case, "uniform" means the same size and shape.

The longest axis of the port of the first branch and the longest axis of the port of the second branch may be oriented parallel to each other.

The longest axis of the port of the first branch and the longest axis of the port of the second branch may be oriented orthogonal to each other.

The ports of the first branch and the ports of the second branch may partially overlap and not be parallel to each other.

The ports of the first and second branches may take various relative configurations. Each configuration may have its own characteristics in terms of loss and dispersion.

The dielectric waveguide may be made of a polymeric material.

According to another aspect, there is provided a method of guiding electromagnetic waves comprising injecting the waves into the dielectric waveguide of claim 1. The two orthogonal polarization components may propagate in opposite directions at the dual polarized port. The two orthogonal polarization components may propagate in the same direction at the dual polarized port.

Drawings

The invention will now be described by way of example with reference to the accompanying drawings. In the drawings:

fig. 1 shows an exemplary configuration of a dielectric waveguide for multiplexing or demultiplexing polarized electromagnetic waves.

Fig. 2 shows a spatial sequence of cross-sections of the exemplary waveguide depicted in fig. 1.

Fig. 3 illustrates a number of exemplary implementations of waveguides in a communication system.

Detailed Description

The proposed dielectric waveguide embodies a novel quadrature analog converter (orthomode transducer, OMT) or connector. In one application, a waveguide receives a signal comprising two orthogonally polarized components and spatially separates the two components. In one embodiment, the waveguide rotates the two components until they become spatially separated signals with parallel polarizations. Obviously, the waveguide may be used as a dual polarized interface between a circular PMF and two single polarized waveguides. To prevent additional coupling loss between the connector and the PMF, the connector may be made of a dielectric material similar to the PMF.

The dielectric waveguide or OMT multiplexes polarization with three physical ports such that one port comprises a combined polarization and the other two ports comprise separate planar polarizations. In the proposed device multiplexing is achieved by a suitable choice of the physical size, shape and arrangement of the waveguides. The dielectric waveguide need not include any internal cross antennas or filters for selecting the planar components of the signal.

Fig. 1 shows an exemplary configuration of a dielectric waveguide 100 for multiplexing or demultiplexing polarized electromagnetic waves. Dielectric waveguides can be used to spatially separate two orthogonally polarized components of an electromagnetic wave from each other. Alternatively, a dielectric waveguide may be used to form an electromagnetic wave having two orthogonal polarization components by spatially combining two linearly polarized electromagnetic waves. The dielectric waveguide comprises a first branch 102 for carrying a first linearly polarized wave and a second branch 104 for carrying a second linearly polarized wave. The dielectric waveguide comprises dual polarized ports 106, said dual polarized ports 106 comprising a first region 108 and a second region 110. The first region 108 and the second region 110 of dual polarized port 106 are the cross-section of first branch 102 and the cross-section of second branch 104, respectively. The first region 108 and the second region 110 partially overlap.

In the example shown, the first region 108 and the second region 110 intersect orthogonally to one another such that the longest axis of the first region and the longest axis of the second region are at right angles to one another. That is, the first region 108 and the second region 110 overlap to form a cross-shaped (e.g., "+" shaped) cross-section. In operation, respective components of the dual polarized electromagnetic wave are confined within respective first and second regions of the waveguide. The physical dimensions of the waveguides limit polarized waves in an orthogonal arrangement. The relative positions and orientations of the two separate linearly polarized waves present in the first and second branches 102, 104 may be changed in a progressive manner such that they are combined while following the physical constraints of the waveguides, ultimately combining to form a single dual polarized wave.

In this application, the word "port" refers to a cross section of a waveguide or a cross section of a waveguide branch. The ports are not necessarily located at the ends of the waveguides. That is, the particular cross-section referred to by the term "port" may be located anywhere along the waveguide.

The first branch 102 has a port 112 remote from the dual polarized port 108. Similarly, the second branch 104 has a port 114 remote from the dual polarized port 108. In this example, ports 112 and 114 are each located at an end of a respective branch.

A dielectric waveguide is a waveguide that consists entirely or predominantly of dielectric material. Electromagnetic waves (e.g., millimeter waves or microwaves) may propagate in a dielectric medium where they are guided by the outer boundary of the medium, i.e., by the geometry of the medium. The wavelength range in which the guiding effect is achieved corresponds approximately to the dimensions of the waveguide. Generally, the higher the dielectric constant, the better the guiding effect, but the higher the loss. The dielectric waveguide may be made of a polymeric material.

In one use example, the waveguide makes the antennas (not shown) at the ends of the first and second branches 102, 104 one-dimensional antennas. The two one-dimensional antennas may even be the same single antenna coupled to the two branches comprising the linearly polarized wave, respectively. In this way, a single antenna may be used to input the same linearly polarized wave through both the first and second branches, and these waves may then be multiplexed together to provide a dual polarized wave for transmission. The dual polarized wave may then be demultiplexed at the far end to retrieve two linearly polarized components comprising the same linear wave.

Alternatively, the input antennas for the first and second branches 102, 104 may be oriented orthogonal to each other such that the input linearly polarized waves are orthogonal to each other before entering the waveguide. Thus, the two linearly polarized signals may not need to be rotated relative to each other within the waveguide in order to combine the two waves to form a single dual polarized wave having orthogonal components. That is, the two linearly polarized waves may already be spatially oriented with respect to each other such that they are orthogonal, but still in separate branches, and then only need to be brought together such that they intersect each other without relative rotation. Thus, the dielectric waveguide may be configured such that the ports of the first branch and the second branch are oriented orthogonally to each other (not shown).

The dielectric waveguide may be configured such that the first branch and the second branch are symmetrical to each other under reflection in a plane passing through the dual polarized port. For example, a plane may pass through the center of a dual polarized port between branches, or halfway through both branches, such that the physical shape of the branches is symmetrical in the plane. Thus, the two polarization components may propagate symmetrically and characteristics such as loss, dispersion and polarization may remain the same or as similar as possible in the two branches. Similarly, the dielectric waveguide may be configured such that the ports of the first branch and the ports of the second branch are oriented parallel to each other.

Fig. 2 shows a sequence of ports or cross sections of the waveguide shown in fig. 1. The sequence starts with (a) having ports for receiving or transmitting dual polarized waves and ends with (e) having two separate ports for receiving or transmitting two separate linearly polarized waves. The ports or cross sections are shown such that the propagation direction of the polarized wave is perpendicular to the plane of the page. I.e. all polarized waves are transmitted in one direction into or out of the page.

In fig. 2 (a), port 106 is a cross section of the waveguide at the location within the waveguide where dual polarized waves are transmitted. Dual polarized port 106 may have C4 symmetry. This means that the dual polarized port is unchanged when rotated 90 degrees around its center. That is, if rotated by an integer value of 90 degrees around the longitudinal axis of the waveguide at the dual polarized port, where the longitudinal axis is an axis parallel to the direction of propagation of the electromagnetic wave at the dual polarized port, the ports look identical. However, a port with C4 symmetry does not necessarily have reflective symmetry along any axis in the port plane. In other words, the first region 108 and the second region 110 (i.e., the cross-section of the first branch 102 and the cross-section of the second branch 104 at the dual polarized port 106) may be uniform and arranged at an angle of 90 degrees with respect to each other. Wherein, "uniform" means the same size and shape. Dual polarized port 106 with C4 symmetry supports electromagnetic waves to be highly symmetric and can achieve good transmission characteristics of the waveguide.

Dual polarized port 106 may have D4 symmetry. D4 symmetry is the same as the symmetry order of the squares. For example, the dual polarized port may be cross-shaped, or clover-shaped. D4 symmetry has the advantages of C4 symmetry described above. Furthermore, the dual polarized port has two orthogonal reflection axes, which are symmetrical under reflection from either of these two axes.

Parts (b) to (d) of fig. 2 show the ports of the waveguide as a first branch 102 comprising a first region 108 and a second branch 104 comprising a second region 110, which branches are gradually spatially separated from each other. By separating the two waves confined within the first region 108 and the second region 110, respectively, in a progressive manner, distortion and loss may be minimized. The degree of gradual separation depends on the frequency and wavelength of the wave, the index of reflection of the dielectric from which the waveguide is made, and the sharpness of the bend in the waveguide boundary.

In parts (c) to (e) of fig. 2, it can also be seen that the cross section of the first branch 102 and the cross section of the second branch 104 are gradually rotated in space relative to each other. Thus, when two waves propagate in both branches, the polarization vector of the wave in the first branch 102 and the polarization vector of the wave in the second branch 104 gradually rotate relative to each other. In one embodiment, the two vectors rotate from a 90 degree relative angle at the dual polarized port to a 0 degree or 180 degree relative angle between the port 108 of the first branch and the port 110 of the second branch.

In fig. 2 (e), it can be seen that the first port 108 of the first branch 102 and the second port 110 of the second branch 104 are spatially separated from each other. This physical separation facilitates the complete separation of the two orthogonally polarized components of the electromagnetic wave. It also helps to connect the waveguide to two spatially separated devices, one for each component. For example, the two spatially separated devices may be two separate and distinct antennas. The two spatially separated devices may be two waveguides (in particular two single polarization waveguides), or two transceivers, or one receiver and one transmitter. In this context, the word "spatially separated" means non-intersecting and non-overlapping.

Fig. 3 illustrates a number of exemplary implementations of waveguides in a communication system. As described above, the waveguide may be used to multiplex or demultiplex waves. It should therefore be appreciated that the waveguide may be implemented at one or more ends of the communication path in a variety of ways depending on the signal requirements and its purpose. The waveguides may be used in the following different Tx/Rx configurations.

Part (a) of fig. 3 shows a waveguide implemented in a dual polarized transmission system. The waveguide acts as a polarization combiner on the Transmit (TX) side and as a polarization splitter on the Receive (RX) side.

Part (b) of fig. 3 shows a waveguide implemented in a single polarization transmission system. The waveguide acts as an orthogonal polarization signal splitter on the receiver side, for example in a setting where the polarization of the received signal is unknown.

Part (c) of fig. 3 shows the waveguide implemented at the transmitter side of the system. In the example shown, the signal from the transmitter Tx is split by a splitter into two spatially separated signals. The two spatially separated signals are injected into two spatially separated ports of two branches of the waveguide. These two signals propagate in two branches towards the dual polarized port. At the dual polarized port, the polarizations of the two signals will be orthogonal to each other.

Part (d) of fig. 3 shows the waveguide implemented in a typical duplex use case. In this example, two orthogonal components of the dual polarized wave are used for the transmit and receive components of the communication.

Thus, depending on the requirements of the various implementations, the dielectric waveguide may be configured such that the ports of the first branch and the second branch are identical and have the same orientation. Thus, two ports may be particularly suitable for receiving or transmitting two waves having the same polarization (i.e. having parallel polarization vectors). For example, the two ports may each have an elongated shape, such as an oval or rectangle. In this case, "uniform" means the same size and shape.

The waveguide presented herein is configured as a method for guiding electromagnetic waves. A method of guiding electromagnetic waves includes injecting waves into a dielectric waveguide configured as described herein. The injected electromagnetic wave may be a dual polarized wave having two orthogonal polarized components. The two orthogonal polarization components may be a transmit wave and a receive wave, respectively. The two orthogonal polarization components may be two transmit waves, or the two orthogonal polarization components may be two receive waves. Two orthogonal polarization components may be received at the dual polarized port through the first branch and the second branch, respectively.

The injected electromagnetic wave may be a first linearly polarized wave or a second linearly polarized wave. The first linearly polarized wave and the second linearly polarized wave may be a transmission wave and a reception wave, respectively. The first linearly polarized wave and the second linearly polarized wave may be two transmitted waves, or the two orthogonally polarized components may be two received waves.

The waveguide described above provides the advantage that any coupler design can be supported by the waveguide as a multiplexer. There is no necessary compromise in polarization alone. Furthermore, the proposed simpler and more flexible geometry than the existing methods can be more easily integrated into printed circuit boards or chip packages. Any shape may be implemented that conforms to the space available on the circuit board. Nor does it compromise the performance of the coupling to achieve the necessary shape. Furthermore, the dual polarization coupling efficiency is substantially dependent on the geometry of the waveguide as a multiplexer. This is due to the nature of the coupling mechanism between linearly polarized waves. Furthermore, there is no need to redesign the waveguide to accommodate different substrates, frequency bands or bandwidths. When these parameters are changed, the waveguide remains unchanged as the basic mechanism of the multiplexer or demultiplexer.

The waveguides described above may be implemented in systems that include dielectric waveguide cables (also referred to as polymer microwave fibers) having various cross-sections. For example, the cable or fiber cross-section may be cross-shaped to conform to the dual polarized ports of the waveguide. Alternatively or additionally, the cable may have an oval cross-section. Other cross-sectional shapes may be employed, such as square, rectangular, or circular. One axis of the cable cross section may be sized relative to another orthogonal axis of the cable cross section to minimize or stop relative rotation of the dual polarized signal inside the waveguide cable.

Applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features. Such features or combinations can be implemented as a whole in accordance with the present specification, irrespective of whether such features or combinations of features solve any problems disclosed herein, or not by means of common knowledge of a person skilled in the art; and do not limit the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. Various modifications may be made within the scope of the invention, as will be apparent to those skilled in the art in view of the foregoing description.

Claims (16)

1. A dielectric waveguide (100) for spatially separating two orthogonally polarized components of an electromagnetic wave from each other or for forming an electromagnetic wave having two orthogonally polarized components by spatially combining two linearly polarized electromagnetic waves,

the dielectric waveguide comprising a first branch (102) for carrying a first linearly polarized wave and a second branch (104) for carrying a second linearly polarized wave,

the dielectric waveguide has dual polarized ports (106), the dual polarized ports (106) comprising a first region (108) and a second region (110) that partially overlap, the first region and the second region being a cross-section of the first branch and a cross-section of the second branch, respectively.

2. The dielectric waveguide of claim 1, wherein the dual polarized port has C4 symmetry.

3. The dielectric waveguide of claim 1, wherein the dual polarized port has D4 symmetry.

4. A dielectric waveguide according to any one of the preceding claims, wherein the first and second branches are progressively spatially separated from each other.

5. A dielectric waveguide according to any one of the preceding claims, wherein the first and second branches each have an elongate cross-section.

6. A dielectric waveguide according to any of the preceding claims, wherein at least one of the cross-section of the first branch and the cross-section of the second branch is progressively rotated spatially.

7. The dielectric waveguide of any of the preceding claims, wherein the first and second branches are symmetrical to each other under reflection through a plane of the dual polarized port.

8. The dielectric waveguide according to any of the preceding claims, characterized in that the port (112) of the first branch and the port (114) of the second branch are spatially separated.

9. The dielectric waveguide of claim 8, wherein the port of the first branch and the port of the second branch are identical and have the same orientation.

10. A dielectric waveguide according to claim 8 or 9, wherein the longest axis of the port of the first branch and the longest axis of the port of the second branch are oriented parallel to each other.

11. A dielectric waveguide according to claim 8 or 9, wherein the longest axis of the port of the first branch and the longest axis of the port of the second branch are oriented orthogonally to each other.

12. The dielectric waveguide of any of claims 1 to 7, wherein the ports of the first and second branches partially overlap and are not parallel to each other.

13. A dielectric waveguide according to any of the preceding claims, characterized in that the dielectric waveguide is made of a polymer material.

14. A method of guiding electromagnetic waves, characterized by comprising injecting the waves into a dielectric waveguide (100) as claimed in claim 1.

15. The method of claim 14, wherein the two orthogonal polarization components propagate in opposite directions at the dual polarized port.

16. The method of claim 15, wherein the two orthogonal polarization components propagate in the same direction at the dual polarized port.

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